Nonmarine Bivalves from the Lower Permian (Wolfcampian) of the Chama Basin, New Mexico Spencer G

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Nonmarine bivalves from the Lower Permian (Wolfcampian) of the Chama Basin, New Mexico Spencer G. Lucas and Larry F. Rinehart, 2005, pp. 283-287 in: Geology of the Chama Basin, Lucas, Spencer G.; Zeigler, Kate E.; Lueth, Virgil W.; Owen, Donald E.; [eds.], New Mexico Geological Society 56th Annual Fall Field Conference Guidebook, 456 p.

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SPENCER G. LUCAS AND LARRY F. RINEHART New Mexico Museum of Natural History, 1801 Mountain Road NW, Albuquerque, NM 87104

ABSTRACT.—The Welles quarry is an Early Permian (Wolfcampian) vertebrate fossil locality developed in a pond deposit in the El Cobre Canyon Formation of the Cutler Group near Arroyo del Agua, Rio Arriba County, New Mexico. We describe an extensive assemblage of thin-shelled, freshwater bivalves from the quarry preserved as external and (rarely) internal casts. Typical preservation is with the paired valves wide open (~180o), the hinge intact, and exterior surfaces facing upward. The clams are equivalved, inequilateral, and elongate oval in shape. Ligaments are external and opistodetic, hinges are straight and edentate, and adductor muscle scars are absent or not preserved. Length ranges from ~ 1 to ~ 23 mm. Umbones are slightly inﬂated and located at ~ 0.25 of length from the anterior end. Ornamentation consists only of concentric growth ridges. Two variants, one with a rounded posterior end, and the other more blunt, may represent sexual dimorphs. Allometric height-to- length ratio (≈ 0.45) and overall morphology are essentially identical to the Late Permian anthracosiid Palaeanodonta parallela (Amalitzky), known from South Africa and Russia. However, due to the large temporal and geographic range differences between P. parallela and the Welles quarry specimens, we provisionally assign them to P. cf. P. parallela. This is the ﬁrst report of Palaeanodonta from the Permian of North America, a substantial extension of its stratigraphic range from the Middle Perm- ian to nearly the base of the Permian and suggests that too little is known of late Paleozoic nonmarine bivalves for them to be of great biostratigraphic utility.

INTRODUCTION able for examination in our sample. Considerable lateral com- pression of the fossils is evident and probably occurred during In 1877, David Baldwin discovered fossil vertebrates in Lower compaction of the muddy shale matrix. Many of the impressions Permian strata of the Cutler Group near Arroyo del Agua, Rio show evidence of crushing before the dissolution of the shells Arriba County, New Mexico. Subsequent collecting in the early (Fig. 2D). We believe that the width of the specimens has been part of the 20th Century, especially by field parties from the Uni- artificially reduced, so we do not include it in the morphomet- versity of California at Berkeley, revealed numerous bonebeds rics. Two morphological variants are present. One morph shows southeast of Arroyo del Agua that are now among the classic Early a relatively blunt posterior (Fig. 2F) and probably represents the Permian vertebrate fossil localities in North America (Langston, female form. The other more rounded-posterior morph (Fig. 2G) 1953; Romer, 1960; Berman, 1993). One of these localities is the may represent the males, as in Recent freshwater clams (Johnson, Welles quarry (Fig. 1), a pond deposit that has produced fossils 1947). of fish (Xenacanthus and Progyrolepis), amphibians (Chenopro- The Welles quarry bivalves correspond to the description, diag- sopus, Eryops, Zatrachys and Platyhystrix) and stem reptiles and noses and illustrations of Palaeanodonta parallela (Amalitzky) in pelycosaurs (Diadectes, Sphenacodon and Ophiacodon). Spiri- the literature. Thus, they are equivalved, inequilateral and elon- form coprolites are common in the quarry and probably pertain gated, and they have parallel postero-dorsal and ventral margins, to xenacanth chondrichthyans. The Welles quarry also yields an a vertical to slightly obliquely truncated posterior end, are unor- extensive assemblage of bivalves described here. In this article, namented, have umbones at ~0.25 of length, lack ornamentation NMMNH = New Mexico Museum of Natural History and Sci- except growth rings and have a hinge structure that is straight, ence, Albuquerque. edentate and opistodetic, with external ligament (cf. Amalitzky,

DESCRIPTION AND IDENTIFICATION

During the summer of 2002, we collected several hundred bivalves from the Welles quarry (NMMNH locality 4825). The clams are preserved as high-quality impressions and casts and are cataloged in the NMMNH collections (P-38771 through P- 38790). The fossils frequently occur as isolated individuals but more often in clusters (Fig. 2A). Generally, the valves are attached at the external hinge and are wide open. A few individuals are preserved in dorsal view (Fig. 2C). Internal casts (steinkerns) have been prepared out of a few individuals that were preserved with their valves closed (Fig. 2D). Shell fragments are rare, and when they do occur they are thin and poorly preserved. Internal shell characteristics such as the crossed lamellar structure seen in the Palaeomutelidae can be FIGURE 1. Index map and generalized stratigraphy showing location of important diagnostic features (Silantiev, 1998) but are not avail- Welles quarry. 284 LUCAS AND RINEHART

FIGURE 2. Selected specimens of Palaeanodonta cf. P. parallela from the Welles quarry. All scale bars are in mm. A, NMMNH P-38772, high density cluster of shells. B, NMMNH P-3878B, an individual bivalve in typical preservation aspect (approximately same scale as F). C, NMMNH P-38787, an individual preserved in dorsal view. D, NMMNH P-38789, an internal cast (steinkern). E, NMMNH P-38778, a rare internal mold showing the edentate hinge structure. F, NMMNH P-38785, an individual with the “blunt posterior” morphology, possibly the female form. G, NMMNH P-38781, an individual with the “rounded posterior” morphology, possibly the male form. NONMARINE BIVALVES FROM THE LOWER PERMIAN 285

1895, pl. 13, figs. 5-6b; Cox, 1936, pl. 5, figs. 2-4; Papin and distributions (modes 1 through 8 in the plot). Straight line fits to Doroshenko, 1974, fig. 1; Bradshaw, 1984, fig. 3; Gusev, 1990, p. these components show that they are normally distributed and 183, 188, pl. 9, figs. 21-23). The Welles quarry bivalves are read- that the modes have been correctly resolved. ily distinguished from Anthraconaia, the genus of late Paleozoic The mean values of the resolved modes were then overplot- freshwater bivalve most similar to Palaeanodonta, by the more ted on the growth ring measurement curve (Fig. 4A). The prob- pronounced umbones and the not-as-elongate and not-as-promi- ability plotting method agreed remarkably well with the growth nently rounded anterior lobes (cf. Eagar, 1962, pl. 47; Eagar and ring data and retrieved two additional size classes that show the Peirce, 1993, fig. 4). approach to the growth asymptote. The age of the largest indi- Morphometric analysis also supports assignment of the Welles vidual (assumed to be at or near the asymptote) is somewhat arbi- quarry bivalves to Palaeanodonta parallela. Complex morpho- trarily assigned to 10 years, but could be higher. metric techniques that measure shell curvatures have been pro- Growth in the bivalves appears to fit the standard von Berta- posed for late Paleozoic freshwater bivalves (Papin and Dorosh- lanffy (1938) equation, enko, 1974), but few comparative data exist in this format. We -k•t apply the height-length (h/l) metric, which is ubiquitous in the lit- L(t) = AL•(1-e ) erature and, according to Gusev (1990), is the single most significant diagnostic. We thus compare h/l of the most morphologically where L(t) is length as a function of time, AL is the growth asymp- similar Late Carboniferous and Permian nonmarine bivalves to tote, k is the growth constant, and t is time in years. The small the Welles quarry specimens in a bivariate plot (Fig. 3). All “P.” number of larger specimens leads to difficulty in accurate curve genera are Palaeanodonta, the “A.” genus is Anthraconaia. In the fitting, but at the level of confidence that we can achieve, we

Welles quarry clams, h/l varies from 0.375 to 0.51 and averages approximate AL ≈ 25 mm, and k ≈ 0.1 to 0.15. ≈ 0.45 (the slope of the curve ﬁt line). Palaeanodonta parallela, P. oviformis (Amalitzky) and some others have a similar h/l, but DISCUSSION only P. parallela is comparable in overall size. There are caveats to assigning the Welles quarry bivalves to The order Unionoida, which encompasses most of the non- Palaeanodonta. Deeply incised adductor scars and anterior lobes marine bivalves, originated in the Devonian and persists today that are greater in height than the posterior lobes are characters of (Cox, 1969). Bivalves are long-lived and ecologically important Palaeanodonta. We have no specimens in which muscle scars are elements of freshwater biological systems (Anthony and Down- preserved, and some of our specimens show a taller anterior lobe, ing, 1999). They compete with ﬁsh for food resources; they fre- though others do not. Nonetheless, the Welles quarry bivalves quently constitute the bulk of biomass in streams and ponds, and show greater agreement with Palaeanodonta than any other late are important prey species. Evidence exists that their current Paleozoic freshwater bivalve genus. Indeed, we cannot distin- growth rates, production, and ecological position have been in guish the Welles quarry bivalves from P. parallela, but given place since at least the Triassic (Rinehart et al., 2002). the great geographic and temporal distance between them and Late Paleozoic nonmarine bivalves, including the anthracosi- P. parallela (Late Permian of Russia and South Africa), and the ids, palaeomutelids, and some myalinids (brackish water) had a subtle morphological differences between them, we only assign worldwide distribution. Examples include (but are not limited to): the Welles quarry bivalves to P. cf. P. parallela. the Middle-Upper Permian Karoo Supergroup of southern Africa

GROWTH

Growth of the Welles quarry clams was assessed by two meth- ods: growth ring measurement, and statistical analysis by probability plotting (Fig. 4). Growth ring measurements of an individual are shown by the open squares in Figure 4A. These data form a straight line and do not show the approach to the growth asymptote because the individual was not large enough. On larger specimens, however, the small growth rings near the umbones are difficult to distinguish. So, we used a probability plotting method to resolve the size classes (~ yearly age groups) of the clam population. In the probability plot (Fig. 4B) the lengths of 36 individuals are plotted against a Normal (Gaussian) cumulative probability scale. The filled circles (all data) show a multi-modal distribution of lengths as indicated by numerous concave-up-to-concave-down inflections (King, 1971; Peck, 1987). The component FIGURE 3. Bivariate plot of height versus length for the Welles quarry modes of this multi-modal distribution are resolved by separating bivalves and several Permian and Pennsylvanian species of similar gross the data at the inflection points and replotting them as distinct morphology. The slope of the curve fit is the h/l ratio. 286 LUCAS AND RINEHART

in time and space of all late Paleozoic freshwater bivalves are not well known. This should make us very cautious in using them for biostratigraphy.

ACKNOWLEDGMENTS

The New Mexico State Land Ofﬁce permitted collecting at the Welles quarry. Several NMMNH volunteers assisted in the ﬁeld. Andrew Heckert, Joerg Schneider and Kate Zeigler reviewed the manuscript.

REFERENCES

Amalitzky, W., 1895, A comparison of the Permian freshwater Lamellibranchiata from Russia with those from the Karoo System of Africa: Quarterly Journal of the Geological Society of London, v. 51, p. 337-351. Anthony, J. L., and Downing, J. L., 1999, Extreme longevity in freshwater mus- sels (family Unionidae) infered from mark-recapture growth data (abstract), in Aquatic sciences Meeting of the American Society of Limnology and Oceanography, Santa Fe, NM. Berman, D. S., 1993, Lower Permian vertebrate localities of New Mexico and their assemblages: New Mexico Museum of Natural History and Science, Bulletin 2, p. 11-21. Bertalanffy, L. V., 1938, A quantitative theory of organic growth (inquiries on growth laws. II): Human Biology, v. 10, p. 181-213. Bond, G., 1954, Lamellibranchia and plants from the Lower Karroo Beds of northern Rhodesia: Geological Magazine, v. 91, p. 189-192. Bradshaw, M., 1984, Permian nonmarine bivalves from the Ohio Range, Antarc- tica: Alcheringa, v. 8, p. 305-309. Cox, L. R., 1932, Lamellibranchia from the Karroo Beds of the Ruhuhu Coal- ﬁelds, Tanganyika Territory: Quarterly Journal of the Geological Society of London, v. 88, p. 623-633. Cox, L. R., 1936, Karroo Lamellibranchia from Tanganyika Territory and Mada- FIGURE 4. A, Growth curve for Palaeanodonta cf. P. parallela speci- gascar: Quarterly Journal of the Geological Society of London, v. 92, p. mens from the Welles quarry generated by growth ring measurements of 32-57. Cox, L. R., 1969, Unionoida; in Moore, R. C., ed., Treatise on Invertebrate Pale- one individual (squares) and by probability plot method (dots). B, Prob- ontology (N) Mollusca 6: Lawrence, Kansas, The Geological Society of ability plot of lengths of 36 individuals (dots) and resolved component America and The University of Kansas, p. N401-N470. size classes representing age groups. Davies, J. H., and Trueman, A. E., 1927, A revision of the non-marine lamellibranchs of the Coal Measures, and a discussion of their zonal sequence: Geological Society of London Quarterly Journal, v. 83, p. 210-259. and Madagascar (Amalitzky, 1895; Bond, 1954; Cox, 1932, 1936; Eager, R. M. C., 1962, New Upper Carboniferous non-marine lamellibranchs: Rossouw, 1970); the Permian Mount Glossopteris Formation of Paleontology, v. 5, no. Part 2, p. 307-339. Eagar, R. M. C., 1984, Late Carboniferous-Early Permian nonmarine bivalve the Ohio Mountains, Antarctica (Bradshaw, 1984); North Amer- faunas of northern Europe and eastern North America: Compte Rendu Neu- ica, in the Upper Carboniferous of Nova Scotia (Rogers, 1965) and vième Congrès International de Stratigraphie et de Géologie de Carbonifère, the Upper Carboniferous-Lower Permian of the eastern United Washington and Champaign-Urbana, 1979, v. 2, p. 559-576. States (e.g., Eagar, 1984); the Upper Permian (Tartarian) strata Eagar, R. M. C. and Peirce, H. W., 1993, A nonmarine pelecypod assemblage in the Pennsylvanian of Arizona and its correlation with a horizon in Pennsyl- of the Oka-Volga River Basin of Russia (Gusev, 1990; Silantiev, vania: Journal of Paleontology, v. 67, p. 61-70. 1998); and the Upper Carboniferous Coal Measures of northern Gusev, A. K., 1990, Nemorskie dvustvorchatye molluski verchney Permi Evro- France, England, and Ireland (Davies and Trueman, 1927; Eager, piskoi chasti SSSR (Non-marine bivalves from the Upper Permian of the 1962). Additional assemblages are known from southern Asia European part of the USSR): Kazan, Kazan University Press, 295 p. Johnson, R. I., 1947, Lampsilis cariosa Say and Lampsilis ochracea Say: Occa- (Rossouw, 1970) and South America (Simoes et al., 1998). The sional Papers on Molluscs, v. 1, p. 145-156. genus Palaeanodonta is known from the Middle or Late Permian King, J. R., 1971, Probability charts for decision making: New York, Industrial of Antarctica, South Africa, Kenya, Russia, Burma and Siberia, Press Inc., 290 p. among other places (Amalitzky, 1895; Bradshaw, 1984; Gusev, Langston, W., Jr., 1953, Permian amphibians from New Mexico: University of California, Publications in Geological Sciences, v. 29, p. 349-416. 1990). These are all records of Tatarian age, which is to say they Lucas, S. G., 2004, A global hiatus in the Middle Permian tetrapod fossil record: are Capitanian to Changshingian on the marine timescale (Lucas, Stratigraphy, v. 1, p. 47-64. 2004) and thus much younger than the Welles quarry. Papin, Y. S. and Doroshenko, A. A., 1974, Biometry of the shells of nonmarine The Welles quarry bivalves are the ﬁrst occurrence of Palae- Late Permian bivalves: Paleontological Journal, v. 8, p. 541-547. Peck, D. S., 1987, Accelerated testing handbook: Portola, Technology Associates, anodonta in the North American Permian and they extend the 136 p. temporal range of this genus back to the Early Permian. This sub- Rinehart, L. F., Lucas, S. G. and Heckert, A. B., 2002, Stasis in bivalve growth stantial range extension suggests to us that the true distributions and population ecology: Age distribution, growth curves, and biomass of a NONMARINE BIVALVES FROM THE LOWER PERMIAN 287

population of Revueltian (Upper Triassic: Early-mid Norian) unionids from Rossouw, P. J., 1970, Freshwater Mollusca in the Beaufort Series of South Africa: West Texas: Geological Society of America, Abstracts with Programs, v. 34, Second Gondwana Symposium, Pretoria, South Africa, p. 615-616. no. 6, p. 354. Silantiev, V. V., 1998, New data on the Upper Permian non-marine bivalve Pal- Rogers, M. J., 1965, A revision of the species of nonmarine Bivalvia from the aeomutela in European Russia; in Johnston, P. A. and Haggart, J. W., eds., Upper Carboniferous of eastern North America: Journal of Paleontology, v. Bivalves: An eon of evolution: Calgary, University of Calgary Press, p. 437- 39, p. 663-686. 442. Romer, A. S., 1960, The vertebrate fauna of the New Mexico Permian: New Simoes, M. G., Rocha-Campos, A. C. and Anelli, L. E., 1998, Paleoecology and Mexico Geological Society, 11th Field Conference Guidebook, p. 48-54. evolution of Permian bivalve faunas (Parana Basin) in Brazil; in Johnston, P. A., and Haggart, J. W., eds., Bivalves: An eon of evolution: Calgary, Uni- versity of Calgary Press, p. 443-452.